Conductivity and Polarization Processes in Highly Cross-Linked Supported Ionic Liquid-Like Phases

Abstract

Supported ionic liquid-like phases were prepared by anchoring imidazolium moieties onto highly crosslinked poly(p-chloromethylstyrene-co-divinylbenzene) monolithic matrixes. The influence of the chemical nature of the anions on the response of supported ionic liquid-like phases to electrical perturbation fields was studied by impedance spectroscopy over wide ranges of frequency and temperature. The exchange of the chloride anions (Cl-) by bis(trifluormethanesulfonyl)amide anions (NTf2 -) greatly affects the psychic-chemical properties of the resulting material. The equivalent circuit that describes the impedance response of the SILLP materials used in this study to electrical perturbation fields is a resistance independent of frequency in series with a parallel Rp-CPE circuit. At high frequencies the CPE has the behavior of a capacitance. The ionic conductivity of the system increases 2 orders of magnitude by exchanging Cl- anions for NTf2 -. Despite the apparent high cross-linking degree of the supporter, the systems having imidazolium units with Cl- and NTf2 - as counterions apparently exhibit a glass-liquid transition in the vicinity of 343 K (70 °C) and 313 K (40 °C), respectively. Dipolar relaxations and conductive process are discussed in terms of chain mobility